Tested-by: Carol L Soto cs...@nvidia.com<mailto:cs...@nvidia.com>
From: Nirmoy Das <nirm...@nvidia.com> Date: Thursday, September 18, 2025 at 7:17 AM To: Thomas Zimmermann <tzimmerm...@suse.de>, dri-devel@lists.freedesktop.org <dri-devel@lists.freedesktop.org> Cc: jfale...@redhat.com <jfale...@redhat.com>, mrip...@kernel.org <mrip...@kernel.org>, Carol Soto <cs...@nvidia.com> Subject: Re: [RFC PATCH] drm/ast: Use msleep instead of mdelay for edid read Hi Thomas, On 18.09.25 12:32, Thomas Zimmermann wrote: > Hi > > Am 17.09.25 um 21:43 schrieb Nirmoy Das: >> The busy-waiting in `mdelay()` can cause CPU stalls and kernel timeouts >> during boot. >> >> Signed-off-by: Nirmoy Das <nirm...@nvidia.com> > > Reviewed-by: Thomas Zimmermann <tzimmerm...@suse.de> > >> >> Sending this as RFC as I am familiar with the code and not sure >> if this transition is safe. > > It's only waiting for hardware, so most likely safe. I'll give it a > try before merging the patch. Thanks for this fix. > Perfect. Thanks for also trying it out. We tried it on older kernel and it helped. > There are other calls to mdelay in the driver. Should they be replaced > as well? Haven't observed any issue with those calls which occurs at shorter intervals and may be that is why they didn't cause a blockage. Regards, Nirmoy > > Best regards > Thomas > >> --- >> drivers/gpu/drm/ast/ast_dp.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/gpu/drm/ast/ast_dp.c b/drivers/gpu/drm/ast/ast_dp.c >> index 19c04687b0fe1..8e650a02c5287 100644 >> --- a/drivers/gpu/drm/ast/ast_dp.c >> +++ b/drivers/gpu/drm/ast/ast_dp.c >> @@ -134,7 +134,7 @@ static int ast_astdp_read_edid_block(void *data, >> u8 *buf, unsigned int block, si >> * 3. The Delays are often longer a lot when system >> resume from S3/S4. >> */ >> if (j) >> - mdelay(j + 1); >> + msleep(j + 1); >> >> /* Wait for EDID offset to show up in mirror register */ >> vgacrd7 = ast_get_index_reg(ast, AST_IO_VGACRI, 0xd7); >> -- >> 2.43.0 >> >
