On 08/25/2015 12:15 PM, Laura Abbott wrote > -----Original Message----- > From: Laura Abbott [mailto:labb...@redhat.com] > Sent: Tuesday, August 25, 2015 12:15 PM > To: Zhao Qiang-B45475; Wood Scott-B07421 > Cc: linux-ker...@vger.kernel.org; linuxppc-dev@lists.ozlabs.org; > lau...@codeaurora.org; Xie Xiaobo-R63061; b...@kernel.crashing.org; Li > Yang-Leo-R58472; pau...@samba.org > Subject: Re: [PATCH v6 3/3] qe_common: add qe_muram_ functions to manage > muram > > On 08/24/2015 08:03 PM, Zhao Qiang wrote: > > > >> -----Original Message----- > >> From: Laura Abbott [mailto:labb...@redhat.com] > >> Sent: Tuesday, August 25, 2015 7:32 AM > >> To: Zhao Qiang-B45475; Wood Scott-B07421 > >> Cc: linux-ker...@vger.kernel.org; linuxppc-dev@lists.ozlabs.org; > >> lau...@codeaurora.org; Xie Xiaobo-R63061; b...@kernel.crashing.org; > >> Li Yang-Leo-R58472; pau...@samba.org > >> Subject: Re: [PATCH v6 3/3] qe_common: add qe_muram_ functions to > >> manage muram > >> > >> On 08/24/2015 02:31 AM, Zhao Qiang wrote: > >> > >> > >>> +out: > >>> + of_node_put(np); > >>> + return ret; > >>> +} > >>> + > >>> +/** > >>> + * qe_muram_alloc - allocate the requested size worth of multi-user > >>> +ram > >>> + * @size: number of bytes to allocate > >>> + * @align: requested alignment, in bytes > >>> + * > >>> + * This function returns an offset into the muram area. > >>> + * Use qe_dpram_addr() to get the virtual address of the area. > >>> + * Use qe_muram_free() to free the allocation. > >>> + */ > >>> +unsigned long qe_muram_alloc(unsigned long size, unsigned long > >>> +align) { > >>> + unsigned long start; > >>> + unsigned long flags; > >>> + struct muram_block *entry; > >>> + > >>> + spin_lock_irqsave(&qe_muram_lock, flags); > >>> + muram_pool_data.align = align; > >>> + start = gen_pool_alloc(muram_pool, size); > >> > >> The advantage of creating gen_pool_alloc_data was so that you could > >> pass in the align automatically without having to modify the structure. > >> Is there a reason you aren't using that? > >> > >>> + memset(qe_muram_addr(start), 0, size); > >> > >> There doesn't seem to be a check for allocation failure from the > >> gen_alloc. > > > > gen_pool_alloc will return 0 if there is error, but if the address > > returned is just 0x0, it can't distinguish it is address or error. > > > > Yes, that's a bad limitation of gen_pool. Maybe one day that will get > fixed. > In a previous out of tree driver, I worked around this by offsetting the > gen_pool_add by a constant so any return value was non-zero and out of > memory was zero and then subtracting the constant off of the return value. > Not sure if that's better or worse than just fixing gen_alloc. >
The workaround works for non alignment allocation, but for alignment allocation, It need to align bytes to addr 0, offsetting the gen_pool_add maybe make wrong alignment . > > Thanks, > Laura _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
